Manual navigation method

[Kumando]

Im using Dantenocs method simulating Sextant readings (Ctrl click to fix position) when weather permits of course at sunrise, noon, sunset and midnigt (stars). But what i really want to know is if it was only possible to take measurements at these specific times of the day or as long as there was sun and good weather, the u-boats navigator always managed to fix the position anytime of the day in reality?

[_Seth_]

Hi mate!
Yes, weather was a factor in RL navigation (and has always been). Just watch "das boot", when the navigator tells the captain that he hasnt been able to get a good sun -or star "shot" because of the "sauer wetter". In real life they also use a timetable (dont know its name) to get the times right.
Edit: If they were near land, they could also use "dead-reconing", and use different land-base objects for recognition.

[Kumando]

Yes i know that part of the movie mate, but i would like to know if in clear weather for example its 15:00 PM can i take measurements from the sun at this time?

[Brag]

Sextant readings of the sun can be taken almost any time the sun is showing. Normally you take two shots about 1.5 hours appart to get a running fix. Then, of course, the local noon shot. Star shots are taken during morning and evening twilight as you need to be able to see both stars and the horizon.

Since you only have a few minutes to shoot the stars, the navigator prepares a star forecast, which allows him to preset the sextant based on his DR (dead reckoning positon at the time of the shoot. This way, he can quickly find the star, make a minor adjustement to the micrometer and secord the reading. Usually he will attempt to establish a fix by shooting 7 stars.

[Kumando]

Sextant readings of the sun can be taken almost any time the sun is showing. Normally you take two shots about 1.5 hours appart to get a running fix. Then, of course, the local noon shot. Star shots are taken during morning and evening twilight as you need to be able to see both stars and the horizon.

Since you only have a few minutes to shoot the stars, the navigator prepares a star forecast, which allows him to preset the sextant based on his DR (dead reckoning positon at the time of the shoot. This way, he can quickly find the star, make a minor adjustement to the micrometer and secord the reading. Usually he will attempt to establish a fix by shooting 7 stars.


But in other times than noon, sunrise etc wont be so precise right? I use the wind rose in the map for the sextant simulation(ctrl click) my ideia is use this at the times posted above and only do the ctrl click without the rose at the other times wich will not give me a position so accurate like clicking in the rose. What i need to know is if in the other times is also so accurate to take readings from the sun in reality.

[Corsair]

In reality you can take a measure of the sun anytime, it just makes the calculations a little more complicated than the noon fix, and you would usually need several ones. So in a way you can imho consider they would be less precise.

[Kumando]

Thanks mate :up: what do you think of my idea of not clicking in the rose in other times than noon sunrise etc and just ctrl click and mark the position "by eye?"?

[Brag]

Sextant readings of the sun can be taken almost any time the sun is showing. Normally you take two shots about 1.5 hours appart to get a running fix. Then, of course, the local noon shot. Star shots are taken during morning and evening twilight as you need to be able to see both stars and the horizon.

Since you only have a few minutes to shoot the stars, the navigator prepares a star forecast, which allows him to preset the sextant based on his DR (dead reckoning positon at the time of the shoot. This way, he can quickly find the star, make a minor adjustement to the micrometer and secord the reading. Usually he will attempt to establish a fix by shooting 7 stars.


But in other times than noon, sunrise etc wont be so precise right? I use the wind rose in the map for the sextant simulation(ctrl click) my ideia is use this at the times posted above and only do the ctrl click without the rose at the other times wich will not give me a position so accurate like clicking in the rose. What i need to know is if in the other times is also so accurate to take readings from the sun in reality.

Your sun shots will give you an LOP (line of position, so you estimate your advance for let's say 1.5 hours and move your LOP to that position, take another shot at the sun and this will give you a fix. This should give you a position with an error less than 5 miles. A good star fix, depending of which tables you use, can give you a position within 200 meters

[Brag]

It's a simulation. It should work :D

[Corsair]

If we wanted to get close to reality, we should also take into account the sea state. I have some souvenirs of taking sun fixes on sailboats with some waves, can get a little tricky sometimes to have a precise measure...:D In my old days I start liking the GPS Navmap... although it's always good to know the old tricks in case of power shortage, which can always happen...